Suspended Diamond-Shaped Nanowire with Four {111} Facets for High-Performance Ge Gate-All-Around FETs

A feasible pathway to scale germanium (Ge) FETs in future technology nodes has been proposed using the tunable diamond-shaped Ge nanowire (NW). The Ge NW was obtained through a simple top-down dry etching and blanket Ge epitaxy techniques readily available in mass production. The different etching selectivity of surface orientations for Cl₂ and HBr was employed for the three-step isotropic/anisotropic/isotropic dry etching. The ratio of Cl₂ and HBr, mask width, and Ge recess depth were crucial for forming the nearly defect-free suspended Ge channel through effective removal of dislocations near the Si/Ge interface. This technique could also be applied for forming diamond-shaped Si NWs. The suspended diamond-shaped NW gate-all-around NWFETs feature excellent electrostatics, the favorable {111} surfaces along the {110} direction with high carrier mobility, and the nearly defect-free Ge channel. The pFET with a high I_ON/I_OFF ratio of 6 × 10⁷ and promising nFET performance have been demonstrated successfully.